Process of impregnating wood



Patented Nov. 8, 1 9 27. I

JOSEPH IR. COOLIDGE, 31), OF BROOINE, MASSACHUSETTS, ASSIQNOR TO MONTAN', INQ,

0F BOSTON, MASSACHUSETT$, A COBPORATIOS OF MASSACHUSET'Ifi,

rao'cnss or rmranens'rme woon.

I No Drawing.

This invention relates to impregnated woods and to methods of impregnating woods. In my Patent No. 1,556,570, granted October 6, I925, I have disclosed a method of treating wood with a high melting point wax, either alone or in combination with certain fungicides or other materials, which immensely improves the characteristics of the wood. This treatment makes the Wood waterproof, it prevents itfrom shrinking and swelling, and protects it from decay. .Furthermore, these effects are substantially permanent. The invention therefore represents an important advance in this art.

Thepresent invention aims further to improve the process disclosed .imslaid patent with a view -to reducing the time requlred and the expense involved in elf-(acting the impregnation, and making the process more adaptable for practice in the present commercial wood treating plants.

The more important woodtreating plants now in operation are equipped wth pressure cylinders and are designed fundamentally for the impregnation of wood wth creosote. This impregnation usually is carried on at a temperature of between 180 F. and 190? F In impregnating wood with Montan wax or with a mixture of Montan wax and creosote, in accordance with my prior patent, it is preferable to force the impregnat-' ing material into the wood at a temperature of from 220F. to 240 F. The latter tem: perature is rather close to the point at which the structure of the wood wil be impaired if the temperature is maintained for a long period, so that there is danger of injuring the wood unless the temperature is controlled very accurately. Moreover, the fact that the Application filed January 26, 1926. Serial No. 83,961.

ing with the Montan wax, or with the im pregnating compound in which it or one of its substitutes is'the chief ingredient, aliquid which will readily penetrate the wood and which is either a solvent for the wax or is readily miscible with the melted wax. Liquids Wl'llCll are suitable for this purpose are carbon tetrachloride, turpentine, kerosene or gasolene. Another liquid which I have found very satisfactory is a distillate Ob- I tained ,-':from the fractional distillation of petroleum, and which, I understand, comes off between gasolene and kerosene.- This oil has properties somewhat like those of a mixture of kerosene and naphtha, and it is used very widely in the paint trade as a substi-- tute for turpentine. A grade of this oil with which I have obtained very satisfactory results is on the-market under the name of atures the unions of the other liquids and.

Montan wax act like solutions. They may,

however, -be simply very intimate mixtures.

- All of the liquids just mentioned are volatile and they all penetrate the wood very rapidly. Ten to fifteen percent of one of these liquids added 'to the Montan wax permits a reduction in temperature during impregnation to approximately the temperatures ordinarily used in impregnating wood with creosote. From considerations .of economy and safety I prefer to use the petroleum distillate above mentioned, and with ten or 'fifteen percent of this material the im regnating process may be carried out exact ysas descrlbed in my patent. above designated I except for the difference in temperature. Of

course a larger or smaller ercent'age of the solvent maybe used 'depen ing upon the results desired. Uusally it is preferable to eflect the im regnation with as high a concentratio'n o the constituents; which are ,to

remain permanently in the wood 'as-can' be f used and still treat at a suitable temperature and in a satisfactor length of time. The concentration may a so be varied in accordance with'the quantity of wax which it is desired, to leave in the wood. Where the chief object is to reduce the time required to effect the impregnation, the treatment may be carried on at a higher temperature, say for example, 225 to 240 F., and in such a case the oil or solvent added is of great I value in promoting penetration'and therefore shortening the time required for the treatment. I

When the impregnation has been effected and the wood has been removed from the cylinder, the impregnating compound 1s sealed in the wood by the cooling thereof. The volatile ingredient of the impre atmg com ound subsequently evaporates, caving the ontan wax, creosote, or other constitucuts of the treating material permanently 'sealed in the pores and tracheids of the wood.

Some compounds suitable for this purpose may not be volatile, and it is not-essential that they should be so long as they are readily miscible with the wax, penetrate the wood rapidly, and do nothave any substantial adverse effect on the more important characteristics of the treating material. is important for nearly all purposes for which impregnation is effected that the imcom ound will not ooze from pregnatin thetreat woo and will notsoften suflif ciently in the wood at high atmospheric temperatures to produce a moist ortac surface. The surface of wood used out of oors, and even that of much of the wood used in doors, is very likely to attain a temperature of at least 120 F. at certain times, as for example, in the heat of asummer sun. Consequently, it. is important that any of the constituents used with the Montan wax, or its substitutes should not result in permanently reducing the softening point of the material to a temperature below 120 F. In other words, the surface of the treated wood should remain hard andinon tacky at all tempera tures below 120 F. This fact should be borne in mind in reparing the impregnating compound. T e oils which have been mentioned as solvents are substantially inert so far as toxicity is concerned, but either the wax or the solvent used with it may be made toxic if desired by adding suitable a ents such, for example, betanapthol. 'fiiis is .a concentration of the more toxic constituents of creosote oil. Three percent of beta nafithol added to the treating'solution c it sufiiciently toxic to protect the will ma wood from decay. I Theiprocess provided by thi'sin'vention, by

permitting impregnation at 'alower temperature; or by reducing the time required for the treatment at a higher temperature, economizes heat; and in the latter case it permits an increased productionfrom a given plant.

It'is also readily adaptable to the present commercial treating plants. By treating with a lower temperature the den or of injuring the structure of the wood ue to variations in control is practically eliminated.

Furthermore, even when ahigh temperature i I is used the fact that the time of treatment required for this process is very short, also practically eliminatesthe danger of injuring the structure of the wood since a treatment carried on at 250 F. for a short time,'wi1l not damage the wood. This rocess may also be used'to advantage in t e treatment of fibre board, some grades-of which are very diflicult to treat without the use of a solvent or a liquid which is miscible with the melted wax.

While I prefer to use Montan wax as an essential, and usually the predominating, ingredient of the impregnating compound, carnauba or candelilla waxes have somewhat similar properties and may be substituted for it under some conditions as I'have explained in in prior patent. Montan wax may bev mo 'ified somewhat by methods known to the producing industry, and an ex.-

ample of such a product is known commenciall'y as Romalin wax. The modified wax, however, characteristics of Montan wax.

Having thus described my invention, what I desire to claim as new is:

1. That improvement in the process of impregnatingwo od, fibreboard and the like, WhlCh consists in mixing a melted waxy maappears to retain all theessential terial having a softening 'point above F.

with a substantial percentage of an' inert liquid which is miscible with said melted waxy material, and forcing isaid mixture into the pores of the material" being treated for a substantial depth. 3

2. That'improvement in the process of imtile liquid which is misci 1e with said melted waxy material, and subsequently allowing said 1i uid to evaporate.

4. at improvement in the process of treating wood which consists inforcing into the pores and tracheids of the wood a melted mixture of a toxic preservative, a waxy substance which is hard and non-tacky at telniii 1,648,294 I I a peratures below 120 F. and a substantial percentage .of a solvent for said waxy subpregnating wood, fibreboard and the like,

which consists in forcing Montan wax' dissolved in a solvent therefor into thepores of said material, and subsequently allowing 10 the solvent to evaporate.

' 6. That improvement in the process of treating wood which consists in forcing into the pores andtracheids of the wood for a substantial depth and impregnating material 15 consisting essentially of Montan wax and a highly penetrative solvent for said wax.

JOSEPH R. COOLIDGE, III. 

